1. Field
The present disclosure relates generally to optical signals and, in particular, to the transmission of optical signals. Still more particularly, the present disclosure relates to controlling the transmission of optical signals in an optical communications system.
2. Background
Optical signals are electromagnetic waves in one of the ultraviolet spectrum, visible light spectrum, or infrared spectrum. Optical signals in the ultraviolet spectrum have wavelengths from about 10 nanometers to about 400 nanometers. Optical signals in the visible light spectrum have wavelengths from about 400 to about 750 nanometers. Optical signals in the infrared spectrum have wavelengths from about 750 nanometers to about 300 micrometers.
Optical signals are transmitted between devices in an optical communications system. An optical communications system includes sources, receivers, and media. The sources transmit the optical signals to the receivers through media.
The sources may include optical transmitters, such as light emitting diodes, laser diodes, and other suitable optical transmitters. The receivers may include optical receivers, such as optical detectors and other suitable types of optical receivers. These may include, for example, air, a vacuum, fiber optic cables, optical wires, and/or other suitable types of channels for transmitting optical signals. When the media is air, the optical communications system is a wireless optical communications system.
Wirelessly transmitting optical signals from an optical transmitter to a receiver may depend on having a line of sight between the optical transmitter and the receiver. A line of sight is a path without any objects in the media between the optical transmitter and the receiver. Objects in the media may cause the receiver to operate as if the optical signals received at the optical receiver contain information that is not actually present. Further, objects in the media may cause the receiver to not receive some or all of the information in the optical signals received.
A line of sight may not be needed if repeaters are used. These repeaters may be optical-electro-optical (OEO) repeaters. An optical-electro-optical repeater receives an optical signal, converts it into an electrical signal, and then transmits an optical signal.
Wireless optical communications systems provide an alternative to using radio frequency (RF) wireless networks for communications. Radio frequency signals have frequencies between about 30 megahertz and about 300 gigahertz. Radio frequency wireless networks have a potential for radio frequency interference, radio frequency jamming, and other types of disruptions to communications. Further, radio frequency signals are more easily detected than optical signals.
However, optical signals may have a greater rate of attenuation as compared to radio frequency signals. Attenuation is the rate at which an optical signal is reduced in intensity as it propagates through a medium.
Therefore, it would be desirable to have a method and apparatus that may overcome one or more of the issues described above, as well as other possible issues.